For example, a center pillar and a rocker are connected to each other at a side part in a substantially center position of a vehicle in the longitudinal direction. As the side part structure of the vehicle, for example, there is known a side part structure of a vehicle shown in FIG. 7. The side part structure of the vehicle shown in FIG. 7 is provided with a center pillar 71 that extends from a side part of a vehicle in the vertical direction. Further, the lower end of the center pillar 71 is connected to a rocker 72 that extends in the longitudinal direction. Further, in the connection portion between the center pillar 71 and the rocker 72, the surface of the rocker 72 is covered at the lower end of the center pillar 71.
Further, in the side part structure of the vehicle, a method has been examined which decreases the deformation amount of an interior of a vehicle by distributing collision energy to an entire vehicle body through a front door or a center pillar when a side collision occurs in the vehicle. For this reason, for example, as a reinforcement member of the center pillar, there is known a pillar reinforcement structure including a pillar reinforcement having a thick plate portion disposed at the upper side of the length direction of the center pillar and a thin plate portion disposed at the lower side thereof and having a thickness thinner than that of the thick plate portion (for example, refer to Patent Literature 1). In the pillar reinforcement structure, a bonding portion between the thick plate portion and the thin plate portion is located at a bottom position of the center pillar. Further, as for the pillar reinforce, an inner member is disposed to extend in the vertical direction over the bonding portion, and the lower end of the inner member is disposed between the bonding portion and the rocker portion.    Patent Literature 1: JP-A-2002-347655